Current limiting circuit breaker



Nov. 24, 1964 B. A. PITEO 3,158,711

CURRENT LIMITING CIRCUIT BREAKER Filed Aug. 23, 1962 42 INVENTOR.

BENJAMIN A. P/rea (/e.

BYWM ITG w A T TOR/V5 Y United States Patent 3,158,711 CURRENT LTMITKNG CIRCUlT EREAKER Benjamin A. Piteo, Forestvilie, Coma, assignor to General Electric Company, a corporation oi New York Filed Aug. 23, 1962, Ser. No. 218,945 3 Claims. (Cl. 200-87) My invention relates to electric circuit breakers, and particularly to current limiting" electric circuit breakers, i.e., circuit breakers which include means responsive at extremely high speed to short circuit current conditions to limit the rate of rise of short circuit current.

It has been recognized in accordance with the prior art that a particularly effective Way of puoducing a current limiting action in a circuit breaker is to provide means acting directly upon the separable contacts to cause an initial separation prior to the time required for the main mechanism of the circuit interrupter to operate. Thus, it has been known to provide such circuit interrupters including a normally movable and a normally stationary contact, and means for retracting the normally stationary contact upon the occurrence of short circuit current conditions to introduce an initial arc prior to the time required for the movable contact to move to its open position. Such structures, in which the normally stationary contact is retracted to provide an initial contact gap, however, are relatively complicated and expensive.

It is an object of the present invention to provide a current limiting circuit breaker including means for directly moving the movable contact in opening direction upon the occurrence of short circuit current conditions, prior to tripping movement of the mechanism generally.

It is a further important object of the invention to provide a mechanism of this type which includes a movable contact member of the bridging type, providing a doublebreak construction.

In accordance with the invention in one form, an electric circuit breaker is provided including a movable contact member of the bridging contact type having a pair of spaced contacts and normally movable into and out of bridging position between two relatively stationary contacts. Means is also provided for rocking the bridging contact member about one of its contacting surfaces upon the occurrence of short circuit current conditions, whereby to cause an initial separation of the other two contacts prior to opening movement of the mechanism generally.

The invention will be more fully understood from the following detailed description, and its scope will be pointed out in the appended claims.

In the drawing,

FIGURE 1 is an elevation view of a circuit breaker mechanism in accordance with the invention, the parts being shown in the on condition;

FIGURE 2 is a view of the mechanism of FIGURE 1 the parts being shown in the position which they occupy upon the occurrence of high short circuit current conditions, and before the main mechanism has had time to move to its fully open position, and

FIGURE 3 is a fragmentary sectional View taken on the line 3-301. FIGURE 1.

Referring to the drawing, the invention is shown as incorporated in an electric circuit breaker having an incoming line terminal strap and an outgoing line terminal strap 11, carrying stationary contacts 12 and 13 respectively.

A pair of relatively movable contacts 14 and 15 are carried by a bridging contact member 16. The bridging memberlo is movably carried between the spaced side walls of a lower toggle link 1"]. The link 17 is connected by a pivot pin 18 to an upper toggle link 19. The upper "ice toggle link 19 is pivotally connected by a pivot pin 20 to a manually operable closing button member 21.

The manual closing member 21 has a latch portion 22 which is adapted to be releasably held by a latch member 23 pivotally supported at 24. The latch member 23 has an L-shaped extending portion 23A, biased by a compression spring 24 against a stop 25.

For the purpose of operating the latch member 23 to release the manual member 21, an off button 26 is provided having a stem 27 projecting downwardly and having its end portion adjacent the extension 23A of the latch member 23. A compression spring 28 is provided, biasing the oil button toward unactuated position at all times.

The upper toggle link 19 has an offset extension 29 extending beyond the pivot pin 20 and having a portion adapted to engage a pin 30 carried by the latch member 23, on the occurrence of predetermined conditions, for a purpose and in a manner to be described.

For the purpose of providing contact pressure in the closed position, a compression spring 31 is provided between the side walls of the lower toggle link 17 and abutting at one end against a transverse supporting member 32 rigidly mounted between the side walls of the toggle link 17. The other end of the spring 31 abuts against the bridging member 16. The bridging member 16 also has a pair of integral projecting pins or lug portions 33 each extending into a slot 33A at the lower end of the toggle link 17.

For the purpose of moving the bridging contact member 16 and its associated contacts 14 and 15 to open position, a compression spring 34 is provided, seated in a recess 35 of the insulating support or base 36. The links 17 are provided with a generally spherical projection 37 for the purpose of retaining the spring 35. A generally L- shaped bracket 45 is rigidly attached to the contact bridging member 16 and includes a portion extending closely adjacent the lower toggle links 17, for a purpose to be described.

On-Ofi Operation When the parts are in the position shown in FIGURE 1,

the current path through the circuit breaker is as follows: from terminal strap 1@ to stationary contact 12, to movable contact 14, to bridging contact member 16, to movable contact member 15, to stationary contact 13, to terminal strap It will be observed that in this position, the compression spring 31 provides contact pressure urging the bridging contact member is to closed circuit position.

In order to manually open the circuit, the off button 26 is depressed, moving the end of the shaft 27 into contact with the extension 23A, thereby rotating the latch member 23: counterclockwise as viewed, and disengaging the latch member 23 from the latch projection 22 of the manually operable member 21. This permits the entire assembly comprising the manually operable member 21, the upper toggle link 19, the lower toggle link 17, and the bridging contact member 16 all to be moved upwardly by the action of the compression spring 34. The travel of the contact operating assembly in an upward direction is limited by the stop portions 40.

For the purpose of maintaining the toggle links 17-19, in straightened or set condition, a spring 38 is provided surrounding the pin 18 and having one end 38A in contact with the edge of the toggle link 19 and the other end BiiB in contact with the edge of the toggle link 17.

For the purpose of providing a current limiting action upon the occurrence of extremely high current conditions, the contact bridging member 16 is provided with a rigidly attached endwise extending armature 41, and a magnet field piece assembly is provided comprising a pair of pole pieces 42 interconnected by a core 43 (see FIGURE 3). The intermediate portion of the terminal conductor 11 is wound about the core 43 to form a coil 44.

Current Limiting Operation Upon the occurrence of predetermined current conditions in the circuit, the armature 41 is drawn to the pole pieces 42, as shown in FIGURE 2. When this occurs, the movable contact 14 is moved away from the stationary contact 12, although the movable contact 15 remains in contact with the stationary contact 13. When the movable contact 14 moves away from the stationary contact 12, an arc is drawn between these two members. The impedance of this are, which is inserted in the circuit before the current has had time to rise to a substantially great value, immediately inhibits the rate of rise of the current and reduces the peak which it attains.

At the same time, as the armature 41 is drawn to the pole pieces 42, the extension 45 engages the sides of the lower toggle links 17 and forces the toggle linkage 17-19 to collapse toward the right slightly. When this occurs, the extension 29 of the upper toggle link 19, engages the pin 30 of the latch member 23, rotating the latch member 23 counterclockwise, in releasing direction, releasing itfrom the latch 22 of the manually operated member 21. The entire contact operating assembly, comprising the manually operated member 21, the toggle links 17 and 19, and the bridging member 16 are then all free to move upwardly under the influence of the spring 34. Following this, the toggle knee-spring 38 acts to straighten the toggle linkage again, and the parts return to the normal off position which is the same position which they occupy when the latch member 23 is manually released by means of the button 26.

It will also be observed that if the manually operated member 21 is forcibly held in the on position, as shown in FIGURE 2, the parts will nevertheless move to open position, the toggle links 17-19 being moved to a more collapsed condition and permitting the contact bridging member 16 to move upwardly into engagement with the stop members 40. In other Words, the circuit breaker mechanism is trip free that is, it is free to trip regardless of the position of whether the manually operated member is held in the on position.

It will be observed that because of the double-break action of this mechanism, the current is interrupted at two points simultaneously during normal operation, and also during actual interruption of overload or short circuit currents, as the bridging member 16 moves upwardly toward final open position. At the same time, the same bridging member is utilized, in accordance with the invention, to provide an initial are which is inserted in the circuit substantially instantaneously upon the occurrence of predetermined conditions.

While the invention has been shown in only one particular embodiment, it will be readily apparent that many modifications thereof may be made, and I therefore intend. by the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by letters Patent of the United States is:

1. An electric circuit breaker comprising:

(a) a support,

(b) at least two stationary contacts supported on said support in spaced apart electrically isolated relation,

() a movable contact bridging member movably supported on said support and having a pair of contact portions engageable with said stationary contact respectively,

(d) means for moving said movable contact member between an open position in which said contact portions are out of engagement with said stationary contacts and a closed position in which said contact portions are in engagement with said stationary contacts, and

(e) magnetically operable means operable upon said contact bridging member when in said closed circuit position to tilt said contact bridging member about the engagement of one of said contact portions with the corresponding one or" said stationary contacts to move the other of said contact portions away from the other of said stationary contacts whereby to substantially increase the electrical impedance between said stationary contacts.

2. An electric circuit breaker comprising:

(a) a support,

(b) a pair of stationary contacts mounted on said support in spaced apart electrically isolated relation,

(0) a movable contact bridging member having a pair of contact portions engageable with said stationary contacts respectively,

(d) operating means for moving said contact bridging member between an open position in which said contact portions are out of engagement with said stationary contact and a closed position in which said contact portions are in engagement with said stationary contacts,

(e) said operating means comprising means for retaining said contact bridging member in said open position and means for retaining said contact bridging member in said closed position, said means for retaining said contact bridging member in said closed position including a releasable latch member releasably restraining said contact bridging member in said closed position, said operating means also comprising means for moving said contact bridging member from said closed position to said open position upon release of said releasable member,

(f) magnetically operable means operable upon said contact bridging member when in said closed position to rock said contact bridging member about the engagement of one of said contact portions with the corresponding one of said stationary contacts to thereby move the other of said contact portions out of engagement with the other of said stationary contacts whereby to substantially increase the electrical impedance between said stationary contacts, and

(g) means for causing release of said releasable latch member in response to actuation of said magnetically operable means.

3. An electric circuit breaker comprising:

(a) a support,

([2) a pair of stationary contacts mounted in spaced apart electrically isolated relation on said support,

(0) a movable contact bridging member having a pair of contact portions engageable with said stationary contacts respectively,

(d) operating means for moving said contact bridging member between an open position in which said contact portions are out of engagement with said stationary contacts and a closed position in which said contact portions are in engagement with said stationary contacts,

(6) an electro-magnet mounted on said support comprising a magnetic field piece and an electric winding, said winding being electrically connected to one of said stationary contacts,

(1) a magnetic armature connected to said contact bridging member and disposed and arranged to be attracted to said electro-magnet upon the occurrence of predetermined current conditions through said winding,

(g) said operating mechanism including latch means for releasably latching said contact bridging member in said closed position and means for moving said contact bridging member from said closed position toward said open position upon the release of said latch means,

(11) said armature being disposed and arranged so that when said bridging member is in said closed position and said armature is attracted to said electro-magnet, said armature causes tilting of said contact bridging member about the engagement of one or" said contact portions with one of said stationary contacts to move the other of said contact portions away from the other of said stationary contacts to substantially increase the electrical impedance between said stationary contacts, and

(i) means operated by said magnetic armature for causing release of said releasable latch means.

References Cited in the file of this patent UNITED STATES PATENTS Ferguson Sept. 26, 1911 Lemmon Dec. 4, 1928 Baker Dec. 24, 1935 Sommermeyer Sept. 7, 1937 Lloyd Feb. 15, 1944 Murray Oct. 14, 1947 Varichon June 17, 1958 Siebers July 26, 1960 Cole Dec. 11, 1962 

1. AN ELECTRIC CIRCUIT BREAKER COMPRISING: (A) A SUPPORT, (B) AT LEAST TWO STATIONARY CONTACTS SUPPORTED ON SAID SUPPORT IN SPACED APART ELECTRICALLY ISOLATED RELATION, (C) A MOVABLE CONTACT BRIDGING MEMBER MOVABLY SUPPORTED ON SAID SUPPORT AND HAVING A PAIR OF CONTACT PORTIONS ENGAGEABLE WITH SAID STATIONARY CONTACT RESPECTIVELY, (D) MEANS FOR MOVING SAID MOVABLE CONTACT MEMBER BETWEEN AN OPEN POSITION IN WHICH SAID CONTACT PORTIONS ARE OUT OF ENGAGEMENT WITH SAID STATIONARY CONTACTS AND A CLOSED POSITION IN WHICH SAID CONTACT PORTIONS ARE IN ENGAGEMENT WITH SAID STATIONARY CONTACTS, AND (E) MAGNETICALLY OPERABLE MEANS OPERABLE UPON SAID CONTACT BRIDGING MEMBER WHEN IN SAID CLOSED CIRCUIT POSITION TO TILT SAID CONTACT BRIDGING MEMBER ABOUT THE ENGAGEMENT OF ONE OF SAID CONTACT PORTIONS WITH THE CORRESPONDING ONE OF SAID STATIONARY CONTACTS TO MOVE THE OTHER OF SAID CONTACT PORTIONS AWAY FROM THE OTHER OF SAID STATIONARY CONTACTS WHEREBY TO SUBSTANTIALLY INCREASE THE ELECTRICAL IMPEDANCE BETWEEN SAID STATIONARY CONTACTS. 